The EAC configuration flags are covered in FAQ.TXT
Q:Which flags can I use in the external compression scheme "User Defined
MP3 Encoder"?
A:In the field "Additional command line options" you could use
replacements for the selectable options :
%s Source filename
%d Destination filename
%h...%h Text "..." only when "High quality" selected
%l...%l Text "..." only when "Low quality" selected
%c...%c Text "..." only when "CRC checksum" selected
%r Bitrate ("32".."320")
%a CD artist
%g CD title
%t Track title
%y Year
%n Track number
%m MP3 music genre
So a command line would look like (for l3enc)
%s %d -br %r000 %h-hq%h %c-crc%c
The extension can also be selected for this setting.
One way to use two presets, would be to set them as the "high quality" and "low quality" entries, and leave out the bitrate altogether.
If you like to encode at EXTREME, but occasionally want to save a bit more space, you could have EXTREME as HQ and STANDARD as LQ - or if you want archival and portable, maybe EXTREME and something a lot lower (preset (number) is average bitrate).
Some of the other options would need to be used in conjunction with the LAME options for ID3 tagging - to set names and things...